The "TLT" is the engine code..all my books are out in the shop..I tried Moretec and a few other sites,they only list casting #..yours IS listed as a 400,so I'd say you might have a 400,but its got the wrong balancer on it..or maybe its been reworked with a 350 crank??...does the flex plate have any balance weight on it..??.. ---it wouldn't be the first 400 I've seen or heard of,with the wrong balancer or flexplate on it!..

The 400 I have is from a 78 suburban,I yanked it to put in my 74 K20 years ago,and saved it..never took the codes or numbers off it..guess I'll have to look tomorrow in the daylight and see what mine is!..I'll see if my books list a
"TLT" code too...and let you know,if no one else comes up with an answer first..I don't have many truck codes in my books,mostly cars,that begin with "C",like "CTM",etc..but I'll look..

i would seriously look into that balancer, probably even pull the engine apart because of it. if it is in fact a 400 rotating assembly, a neutral balanced damper on it could cause all kinds of problems. specifically in the area of the main bearings.

with that said, did you get my PM on Thursday? i need that bellhousing ASAP!

My book lists a"TLS,and a"TLR"(my 78 is a "TLR") for 400 SB codes in 78..but this is in a Blazer/C/K Series book,a van might have the code a bit different..I'd say its definately a 78 400,the alphabetical order of the code "jives" with the ones I listed ..it just has the wrong balancer,or a different crank perhaps..I'd look inside and make sure it didnt shake itself apart too.,and see if it has a 350 crank in it,making it a 377 cid..

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